Magnetotransport of holes through an AlAs/GaAs/AlAs resonant tunnelling quantum well with a ferromagnetic Ga1–x Mnx As emitter

We have fabricated magnetic III–V compound semiconductor resonant tunnelling diodes (RTD's) based on a (Ga, Mn)As material system. The RTD's contain a ferromagnetic Mn‐doped emitter, where the Mn‐concentration was chosen on both sides of the metal–insulator (M–I) transition. The measured I –V characteristics show that large magnetoresistance (MR) is not present in non‐magnetic RTD's without the Mn‐doping. In the case of the metallic emitter the observed positive MR is interpreted as an evidence of the magnetization‐dependent tunnelling related to the exchange interaction between the hole spins and the localised spins of the 3d electrons in the ferromagnetic (Ga, Mn)As layer. Especially, the contributions from the spin‐dependent tunnelling described by the Tsu–Esaki model and from the tunnelling anisotropic magnetoresistance, which was found recently in magnetic tunnel diodes, are discussed. The measured large MR in the I –V characteristics of the magnetic RTD's, which have an emitter on the semiconducting side of the M–I transition, is explained by a simple series resistance model for the magnetic emitter, where the conduction in the Anderson localized states below the mobility edge becomes magnetic field‐dependent due to the Mn‐doping. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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